The present invention relates to a glass antenna system for vehicles (e.g., automobiles), in which an antenna for receiving AM/FM radio waves and TV waves is formed on an upper part of the rear window glass sheet, while heater strips of a defogger are formed on a lower part of the rear window glass.
There are many automotive glass antenna systems in which the defogger is also used as an antenna for receiving AM/FM radio waves and TV waves In this case, it is necessary to adjust the antenna for each automobile type, since the defogger pattern and a feed line from a direct current power source to the defogger are different in each automobile type and since the antenna receiving property and the like are different by the length of this feed line.
In some glass antenna systems, the antenna pattern (grid) is disposed at a position that is away from the defogger by a certain distance in order to reduce adverse effects (e.g., noise) of the defogger on the antenna system.
U.S. Pat. No. 5,610,619, corresponding to Japanese Patent Laid-open Publication 9-172315, discloses such antenna system for an AM/FM vehicle radio. The antenna grid of this system includes a plurality of equally spaced, horizontal antenna elements, an L-shaped element connected to one of end bus bars, and a T-shaped element extending between the antenna grid and the heater grid.
Japanese Patent Laid-open Publication 2001-168623 discloses another antenna system having a loop element connected to a feed point and upper and lower elements extending from the left side of the loop element. It is described in this publication that the distance between the lower element and the top heater strip is preferably from 30 mm to 50 mm.